WASHINGTON — Amid opposition from top Democrats, President Bush said Monday that he is sending to Congress a free trade agreement with Colombia that he urged lawmakers to approve.

The decision by Bush, who said the pact would help stabilize the region, sets the stage for a contentious debate and vote on Capitol Hill in the heat of the presidential campaign.

Congress has 90 days to consider the legislation under special trade negotiating rules that require an up-or-down vote and do not allow amendments. The Colombian accord was negotiated before Congress decided last year not to renew Bush’s trade promotion authority.

“This agreement will advance America’s national security interests in a critical region,” Bush said at a news conference in the Eisenhower Executive Office Building. “It will strengthen a courageous ally in our hemisphere. It will help America’s economy and America’s workers at a vital time. It deserves bipartisan support from the United States Congress.”

Democratic congressional leaders have repeatedly warned the Bush administration not to send the Colombia pact to Capitol Hill, arguing that the Colombian government has failed to do enough to halt assassinations and kidnappings of trade unionists. They also have urged implementing an overhaul of a program that helps retrain workers who lose their jobs because of international trade before the Colombia deal is considered.

In addition, opponents contend the agreements would result in the loss of U.S. jobs. Proponents say it would open a new market for U.S. goods.

The debate over the proposed agreement has created upheaval in the campaign for the White House.

Mark Penn, chief strategist for Sen. Hillary Rodham Clinton (D., N.Y.), stepped down Sunday after the Wall Street Journal reported he met with the Colombian ambassador to the U.S. to discuss promoting the trade deal, which is opposed by Clinton. Penn is chief executive officer of Burson-Marsteller, a public relations firm that represented the government of Colombia in its effort to have the trade deal ratified by Congress.

The President also is seeking congressional approval of free trade pacts with South Korea and Panama.

Apparel importers that shipped $419 million worth of products made in Colombia to the U.S. in the past 12 months, and textile producers that export millions of dollars of fabrics and yarns to the country, have called on Congress to pass a bilateral trade deal with Colombia to make the duty free benefits permanent. They are now temporary under a regional Andean trade pact that needs periodic renewal.

UNITE HERE, the apparel industry’s main union, vigorously opposes the Colombian trade agreement and has vowed to work for its defeat.

“It is outrageous,” said Bruce Raynor, general president of UNITE HERE. “In the middle of a time when American workers can’t afford to put gas in their cars to go to work, Bush would send an agreement to Congress that will further reduce American jobs.”

House Speaker Nancy Pelosi (D., Calif.) and Rep Charles Rangel (D., N.Y.) criticized the President, saying: “His unprecedented decision to send a free trade agreement to Congress without following established protocols of congressional consultation is counterproductive, jeopardizing prospects for its passage.”

Senate Majority Leader Harry Reid (D., Nev.) said the President is pressing for congressional action “under circumstances that maximize the chances it will fail” because of opposition from the Democratic majority in Congress.

U.S. Trade Representative Susan Schwab told reporters that prospects for the agreement in Congress were good because there were Republicans and Democrats who recognized it was important for U.S. economic interests and for national security.

“When we send up a trade agreement, we never know, quite frankly, how it’s going to play, but no Congress has ever defeated a trade agreement,” Schwab said.